Salicylic acid

Salicylic acid is a colorless, crystalline organic carboxylic acid. It is usually prepared by Kolbesynthesis (aka Kolbe-Schmitt reaction). Salicylic acid functions as a plant hormone.

Properties

Salicylic acid is toxic if ingested in large quantities, but in small quantities is used as a food preservativeand antisepticin toothpaste. The carboxyl group(–COOH) can react with alcohols, forming several useful esters. The ester with methanolis methyl salicylate, also known under the name oil of wintergreen. The hydroxyl group(–OH) can be acetylatedto form acetylsalicylic acid (aspirin). Salicylic acid can also trap oxygen(O₂) and initiate free radicalreactions.

Medicinal uses

Also known as Beta Hydroxy Acid(compare to AHA), salicylic acid is the key additivein many skin-care products for the treatment of acne, callouses and corns, keratosis pilarisand warts. It treats acne by causing skin cells to slough off more readily, preventing poresfrom clogging up. This effect on skin cells also makes salicylic acid an active ingredient in several shampoosmeant to treat dandruff.

The medicinal properties of salicylate (mainly for feverrelief) have been known since ancient times. The substance occurs in the bark of willowtrees; the name salicylic acid is derived from salix, the Latinname for the willow tree.

Image:Aspirin.jpg Aspirin(acetylsalicylic acid or ASA) can be prepared by the esterificationof the phenolic hydroxyl group of salicylic acid.

Subsalicylate in combination with bismuthform the popular stomach relief aid known commonly as Pepto-Bismol. When combined the two key ingredients help control diarrhea, nausea, heartburn, and even gas. It is also very mildly anti-biotic.

Salicylic acid as a plant hormone

Here is a list of some of salicylic acid's properties when acting as a plant hormone. It is interesting to note, in light of these properties, that there is a popular belief that cut flowers will last longer if aspirin(acetylsalicylic acid) is dissolved in their water.

Location, characteristics and occasions for synthesis induction

• Cells returning from water stress
• Released by cells secure in having more than enough nutrients and environmental conditions locally to survive at its current metabolic level (speculative)
• All cells capable of synthesizing
• Has its effect or acts by rapid local increases followed by rapid decreases in levels

Effects

• Retards senescence (regulatory role) – probably by inhibiting Ethylene biosynthesis
• Induces flowering
• Inhibits seed germination – by inhibiting ABA synthesis
• May also block the wound response and act antagonistically to ABA, preventing the wound response from spreading further than necessary (speculative)
• After a survival threat has passed SA quickly removes a plant, organ, tissue or cell from a defensive posture and returns it to normal "relaxed" functioning (speculative)
• Increases cell metabolism rate to take advantage of new complete more advantageous nutrient and environmental conditions (speculative)
• A climactic or sustained level of SA may occur if a cell has reached its peak metabolic levels and may signal that a plant's resources can be turned to growth (speculative)
• This climactic or sustained level of SA may be a prerequisite for the synthesis of Auxin and/or Cytokinin, because only then does a plant know that it has enough resources to turn them to growing bigger (highly speculative)

See also

• Benzoic acid
• Benzene ring
• Phenol
• Aspirin
• Alpha Hydroxy Acid

References

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da:Salicylsyre de:Salicylsäure es:Ácido salicílico fr:Acide salicylique ja:????? lv:Salicilsk?be pl:Kwas salicylowy

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Salicylic+acid Wikipedia article Salicylic acid.